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authorNoralf Trønnes <noralf@tronnes.org>2019-05-06 21:01:30 +0300
committerNoralf Trønnes <noralf@tronnes.org>2019-05-14 17:11:28 +0300
commit03a9606e7feef902979bbc0601d6d93e764f251d (patch)
tree14c3cdd6a72146a03461da62b60d17a539d4ffb6 /Documentation/gpu/todo.rst
parent094aa54f0f9e9185babebf95745d71b07a84321c (diff)
downloadlinux-03a9606e7feef902979bbc0601d6d93e764f251d.tar.xz
drm/fb-helper: Avoid race with DRM userspace
drm_fb_helper_is_bound() is used to check if DRM userspace is in control. This is done by looking at the fb on the primary plane. By the time fb-helper gets around to committing, it's possible that the facts have changed. Avoid this race by holding the drm_device->master_mutex lock while committing. When DRM userspace does its first open, it will now wait until fb-helper is done. The helper will stay away if there's a master. Two igt tests fail with the new 'bail out if master' rule. Work around this by relaxing this rule for drm_fb_helper_restore_fbdev_mode_unlocked() until the tests have been fixed. Add todo entry for this. Locking rule: Always take the fb-helper lock first. v5: drm_fb_helper_restore_fbdev_mode_unlocked(): Use restore_fbdev_mode_force() v2: - Remove drm_fb_helper_is_bound() (Daniel Vetter) - No need to check fb_helper->dev->master in drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check. Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20190506180139.6913-3-noralf@tronnes.org
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diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 06ccff9165d5..66f05f4e469f 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -281,6 +281,14 @@ it to use drm_mode_hsync() instead.
Contact: Sean Paul
+drm_fb_helper tasks
+-------------------
+
+- drm_fb_helper_restore_fbdev_mode_unlocked() should call restore_fbdev_mode()
+ not the _force variant so it can bail out if there is a master. But first
+ these igt tests need to be fixed: kms_fbcon_fbt@psr and
+ kms_fbcon_fbt@psr-suspend.
+
Core refactorings
=================